Introduction to Strontium
Strontium is a chemical element represented by the symbol Sr and atomic number 38. It is a reactive metal, belonging to the group of alkaline earth metals in the periodic table. This element does not occur freely in nature due to its high reactivity, but it is found in minerals such as celestine (strontium sulfate, SrSO₄) and strontianite (strontium carbonate, SrCO₃).
Classification
Strontium is classified as an alkaline earth metal. This categorization places it within a group of highly reactive metals known for their metallic lustre and strong reducing properties. It is distinctly a metal, not a non-metal or a metalloid.
Physical Characteristics
Appearance and Texture
Pure strontium exhibits a silvery-white appearance with a bright, metallic lustre when freshly cut or exposed. Upon contact with air, its surface rapidly reacts with oxygen, forming a dull, yellowish oxide layer, which causes it to tarnish. The metal is relatively soft, being softer than calcium but harder than lead. Its softness allows it to be cut with a knife. The freshly cut surface displays a brilliant shine, similar to polished silver or aluminium, metals commonly observed in utensils and jewellery in Indian households.
State of Matter
At standard ambient temperature and pressure (approximately 25°C and 1 atmosphere), strontium exists as a solid.
Thermal Properties
Strontium has a distinct set of thermal properties:
- Melting Point: 777 °C
- Boiling Point: 1377 °C
These points indicate that strontium remains a solid across a wide range of temperatures well above typical room temperature before transitioning to a liquid and then a gaseous state.